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  <h1>The Mesa 3D Graphics Library</h1>
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<h1>Compilation and Installation using Meson</h1>

<ul>
  <li><a href="#basic">Basic Usage</a></li>
  <li><a href="#cross-compilation">Cross-compilation and 32-bit builds</a></li>
</ul>

<h2 id="basic">1. Basic Usage</h2>

<p><strong>The Meson build system is generally considered stable and ready
for production</strong></p>

<p>The meson build is tested on Linux, macOS, Cygwin and Haiku, FreeBSD,
DragonflyBSD, NetBSD, and should work on OpenBSD.</p>

<p><strong>Mesa requires Meson >= 0.45.0 to build.</strong>

Some older versions of meson do not check that they are too old and will error
out in odd ways.
</p>

<p>
The meson program is used to configure the source directory and generates
either a ninja build file or Visual Studio® build files. The latter must
be enabled via the <code>--backend</code> switch, as ninja is the default backend on all
operating systems. Meson only supports out-of-tree builds, and must be passed a
directory to put built and generated sources into. We'll call that directory
"build" for examples.
</p>

<pre>
    meson build/
</pre>

<p>
To see a description of your options you can run <code>meson configure</code>
along with a build directory to view the selected options for. This will show
your meson global arguments and project arguments, along with their defaults
and your local settings.

Meson does not currently support listing options before configure a build
directory, but this feature is being discussed upstream.
</p>

<pre>
    meson configure build/
</pre>

<p>
With additional arguments <code>meson configure</code> is used to change
options on already configured build directory. All options passed to this
command are in the form <code>-D "command"="value"</code>.
</p>

<pre>
    meson configure build/ -Dprefix=/tmp/install -Dglx=true
</pre>

<p>
Note that options taking lists (such as <code>platforms</code>) are
<a href="http://mesonbuild.com/Build-options.html#using-build-options">a bit
more complicated</a>, but the simplest form compatible with Mesa options
is to use a comma to separate values (<code>-D platforms=drm,wayland</code>)
and brackets to represent an empty list (<code>-D platforms=[]</code>).
</p>

<p>
Once you've run the initial <code>meson</code> command successfully you can use
your configured backend to build the project. With ninja, the -C option can be
be used to point at a directory to build.
</p>

<pre>
    ninja -C build/
</pre>

<p>
Without arguments, it will produce libGL.so and/or several other libraries
depending on the options you have chosen. Later, if you want to rebuild for a
different configuration, you should run <code>ninja clean</code> before
changing the configuration, or create a new out of tree build directory for
each configuration you want to build
<a href="http://mesonbuild.com/Using-multiple-build-directories.html">as
recommended in the documentation</a>
</p>

<p>
Autotools automatically updates translation files as part of the build process,
meson does not do this. Instead if you want translated drirc files you will need 
to invoke non-default targets for ninja to update them:
<code>ninja -C build/ xmlpool-pot xmlpool-update-po xmlpool-gmo</code>
</p>

<dl>
<dt><code>Environment Variables</code></dt>
<dd><p>Meson supports the standard CC and CXX environment variables for
changing the default compiler. Meson does support CFLAGS, CXXFLAGS, etc. But
their use is discouraged because of the many caveats in using them. Instead it
is recomended to use <code>-D${lang}_args</code> and
<code>-D${lang}_link_args</code> instead. Among the benefits of these options
is that they are guaranteed to persist across rebuilds and reconfigurations.

Meson does not allow changing compiler in a configured builddir, you will need
to create a new build dir for a different compiler.
</p>

<pre>
    CC=clang CXX=clang++ meson build-clang
    ninja -C build-clang
    ninja -C build-clang clean
    meson configure build -Dc_args="-Wno-typedef-redefinition"
    ninja -C build-clang
</pre>

<p>
The default compilers depends on your operating system. Meson supports most of
the popular compilers, a complete list is available
<a href="http://mesonbuild.com/Reference-tables.html#compiler-ids">here</a>.
</p>

<p>Meson also honors <code>DESTDIR</code> for installs</p>
</dd>


<dt><code>LLVM</code></dt>
<dd><p>Meson includes upstream logic to wrap llvm-config using its standard
dependency interface.
</p></dd>

<dd><p>
As of meson 0.49.0 meson also has the concept of a
<a href="https://mesonbuild.com/Native-environments.html">"native file"</a>,
these files provide information about the native build environment (as opposed
to a cross build environment). They are ini formatted and can override where to
find llvm-config:

custom-llvm.ini
<pre>
    [binaries]
    llvm-config = '/usr/local/bin/llvm/llvm-config'
</pre>

Then configure meson:

<pre>
    meson builddir/ --native-file custom-llvm.ini
</pre>
</p></dd>

<dd><p>
For selecting llvm-config for cross compiling a
<a href="https://mesonbuild.com/Cross-compilation.html#defining-the-environment">"cross file"</a>
should be used. It uses the same format as the native file above:

cross-llvm.ini
<pre>
    [binaries]
    ...
    llvm-config = '/usr/lib/llvm-config-32'
</pre>

Then configure meson:

<pre>
    meson builddir/ --cross-file cross-llvm.ini
</pre>

See the <a href="#cross-compilation">Cross Compilation</a> section for more information.
</dd></p>

<dd><p>
For older versions of meson <code>$PATH</code> (or <code>%PATH%</code> on
windows) will be searched for llvm-config (and llvm-config$version and
llvm-config-$version), you can override this environment variable to control
the search: <code>PATH=/path/with/llvm-config:$PATH meson build</code>.
</dd></p>
</dl>

<dl>
<dt><code>PKG_CONFIG_PATH</code></dt>
<dd><p>The
<code>pkg-config</code> utility is a hard requirement for configuring and
building Mesa on Unix-like systems. It is used to search for external libraries
on the system. This environment variable is used to control the search path for
<code>pkg-config</code>. For instance, setting
<code>PKG_CONFIG_PATH=/usr/X11R6/lib/pkgconfig</code> will search for package
metadata in <code>/usr/X11R6</code> before the standard directories.</p>
</dd>
</dl>

<p>
One of the oddities of meson is that some options are different when passed to
the <code>meson</code> than to <code>meson configure</code>. These options are
passed as --option=foo to <code>meson</code>, but -Doption=foo to <code>meson
configure</code>. Mesa defined options are always passed as -Doption=foo.
</p>

<p>For those coming from autotools be aware of the following:</p>

<dl>
<dt><code>--buildtype/-Dbuildtype</code></dt>
<dd><p>This option will set the compiler debug/optimisation levels to aid
debugging the Mesa libraries.</p>

<p>Note that in meson this defaults to <code>debugoptimized</code>, and
not setting it to <code>release</code> will yield non-optimal
performance and binary size. Not using <code>debug</code> may interfere
with debugging as some code and validation will be optimized away.
</p>

<p> For those wishing to pass their own optimization flags, use the <code>plain</code>
buildtype, which causes meson to inject no additional compiler arguments, only
those in the C/CXXFLAGS and those that mesa itself defines.</p>
</dd>
</dl>

<dl>
<dt><code>-Db_ndebug</code></dt>
<dd><p>This option controls assertions in meson projects. When set to <code>false</code>
(the default) assertions are enabled, when set to true they are disabled. This
is unrelated to the <code>buildtype</code>; setting the latter to
<code>release</code> will not turn off assertions.
</p>
</dd>
</dl>

<h2 id="cross-compilation">2. Cross-compilation and 32-bit builds</h2>

<p><a href="https://mesonbuild.com/Cross-compilation.html">Meson supports
cross-compilation</a> by specifying a number of binary paths and
settings in a file and passing this file to <code>meson</code> or
<code>meson configure</code> with the <code>--cross-file</code>
parameter.</p>

<p>This file can live at any location, but you can use the bare filename
(without the folder path) if you put it in $XDG_DATA_HOME/meson/cross or
~/.local/share/meson/cross</p>

<p>Below are a few example of cross files, but keep in mind that you
will likely have to alter them for your system.</p>

<p>
32-bit build on x86 linux:
<pre>
[binaries]
c = '/usr/bin/gcc'
cpp = '/usr/bin/g++'
ar = '/usr/bin/gcc-ar'
strip = '/usr/bin/strip'
pkgconfig = '/usr/bin/pkg-config-32'
llvm-config = '/usr/bin/llvm-config32'

[properties]
c_args = ['-m32']
c_link_args = ['-m32']
cpp_args = ['-m32']
cpp_link_args = ['-m32']

[host_machine]
system = 'linux'
cpu_family = 'x86'
cpu = 'i686'
endian = 'little'
</pre>
</p>

<p>
64-bit build on ARM linux:
<pre>
[binaries]
c = '/usr/bin/aarch64-linux-gnu-gcc'
cpp = '/usr/bin/aarch64-linux-gnu-g++'
ar = '/usr/bin/aarch64-linux-gnu-ar'
strip = '/usr/bin/aarch64-linux-gnu-strip'
pkgconfig = '/usr/bin/aarch64-linux-gnu-pkg-config'
exe_wrapper = '/usr/bin/qemu-aarch64-static'

[host_machine]
system = 'linux'
cpu_family = 'arm'
cpu = 'aarch64'
endian = 'little'
</pre>
</p>

<p>
64-bit build on x86 windows:
<pre>
[binaries]
c = '/usr/bin/x86_64-w64-mingw32-gcc'
cpp = '/usr/bin/x86_64-w64-mingw32-g++'
ar = '/usr/bin/x86_64-w64-mingw32-ar'
strip = '/usr/bin/x86_64-w64-mingw32-strip'
pkgconfig = '/usr/bin/x86_64-w64-mingw32-pkg-config'
exe_wrapper = 'wine'

[host_machine]
system = 'windows'
cpu_family = 'x86_64'
cpu = 'i686'
endian = 'little'
</pre>
</p>

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